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An acid polysaccharide, named HP, was produced by endophytic Penicillium javanicum MSC-R1 isolated from southern medicine Millettia speciosa Champ. The molecular weight of HP was 37.8 kDa and consisted of Ara f, Galр, Glcр, Manр, and GlcрA with a molar ratio of 1.09: 3.47: 68.48: 16.59: 8.85. The glycosidic linkage of HP was proven to be →3, 4)-α-D-Glcр-(1→6)-α-D-Manр-(1→, →3, 4)-α-D-Glcр-(1→4)-α-D-Glcр-(1→, →3), →6)-α-D-Manр-(1→4)-α-D-Glcр-(1→, →3), β-D-Galр-(1→3)-α-D-Glcр-(1→, →4), →5)-α-L-Ara f -(1→3)-α-D-Glcр-(1→, →4), →6)-α-D-Manр-(1→4)-α-D-GlcAр-(1→ and →4)-α-D-GlcAр-(1→4)-α-D-Glcр-(1→, →3). Additionally, 250 μg/mL of HP possessed nontoxicity to RAW 264.7 cells and exhibited anti-inflammation activity. HP could significantly restrain the amount of tumor necrosis factor-α, interleukin-6 and NO release in RAW264.7, which property is possibly associated with its abundant glucosidic linkage. These results indicated that HP could be regarded as a ponderable ingredient for the health-beneficial functional foods.

Nanozyme with intrinsic enzyme-like activity has emerged as favorite artificial catalyst during recent years. However, current nanozymes are mainly limited to inorganic-derived nanomaterials, while biomolecule-sourced nanozyme (bionanozyme) are rarely reported. Herein, inspired by the basic structure of natural hydrolase family, we constructed 3 oligopeptide-based bionanozymes with intrinsic hydrolase-like activity by implementing zinc induced self-assembly of histidine-rich heptapeptides. Under mild condition, divalent zinc (Zn

Human milk fat substitutes (HMFSs) are the structured lipids intended for infant formula. It provides energy and essential fatty acid for infant. HMFSs are mainly prepared by enzymatic method. In this study, we aim to explore the potential for producing HMFSs by fermentation using R. opacus. The results indicated that different compounds with chain length from 12 to 18, used as carbon source, could be incorporated into triacylglycerols directly. Polyunsaturated fatty acids in term of ARA, EPA, DHA could enter the kennedy pathway directly and involved in the biosynthesis of triacylglycerols. GC, UPLC-MS and 13C-NMR analysis demonstrated that typical structured lipids β-OPL (40.09%) was synthesized in R. opacus. Transcriptome analysis revealed that β-oxidation, fatty acid elongation and kennedy pathways existed in R. opacus. It was concluded that fatty acid supplied as carbon source could enter the kennedy pathways directly or via the de novo fatty acid biosynthesis pathway depending on the chain length, thus, affect the triacylglycerol species formed in the Rhodococcus opacus.

In the study, monodispersed silver nanoparticles (AgNPs) with an average diameter of 9.57 nm were efficiently and controllably biosynthesized by a reductase from Fusarium solani DO7 only in the presence of β-NADPH and polyvinyl pyrrolidone (PVP). The reductase responsible for AgNP formation in F. solani DO7 was further confirmed as 1,4-α-glucosidase. Meanwhile, based on the debate on the antibacterial mechanism of AgNPs, this study elucidated in further depth that antibacterial action of AgNPs was achieved by absorbing to the cell membrane and destabilizing the membrane, leading to cell death. Moreover, AgNPs could accelerate the catalytic reaction of 4−nitroaniline, and 86.9% of 4-nitroaniline was converted to p-phenylene diamine in only 20 min by AgNPs of controllable size and morphology. Our study highlights a simple, green, and cost-effective process for biosynthesizing AgNPs with uniform sizes and excellent antibacterial activity and catalytic reduction of 4-nitroaniline.

Enzymatic asymmetric amination addition is seen as a promising approach for synthesizing amine derivatives, especially unnatural amino acids, which are valuable precursors to fine chemicals and drugs. Despite the broad substrate spectrum of methylaspartate lyase (MAL), some bulky substrates, such as caffeic acid, cannot be effectively accepted. Herein, we report a group of variants structurally derived from Escherichia coli O157:H7 MAL (EcMAL). A combined mutagenesis strategy was used to simultaneously redesign the key residues of the entrance tunnel and binding pocket to explore the possibility of accepting bulky substrates with potential application to chiral drug synthesis. Libraries of residues capable of lining the active center of EcMAL were then constructed and screened by an effective activity solid-phase color screening method using tyrosinase as a cascade catalyst system. Activity assays and molecular dynamics studies of the resultant variants showed that the substrate specificity of EcMAL was modified by adjusting the polarity of the binding pocket and the degree of flexibility of the entrance tunnel. Compared to M3, the optimal variant M8 was obtained with a 15-fold increase in catalytic activity. This structure-based protein engineering of EcMAL can be used to open new application directions or to develop practical multi-enzymatic processes for the production of various useful compounds.

A novel polysaccharide DG2 was obtained from the Dendrobium officinale endophytic fungus Fusarium solani DO7. The structural characterization and immunological activity of DG2 were investigated. Results showed that DG2 with the molecular weight of 152.8 kDa was composed of Galp, Manp, Glcp and Araf at a molar ratio of 4.3:1.9:2.8: 1.0. The main linkage types of DG2 were (1 → )-β-D-Glc, (1 → 4)-β-D-Glc, (1 → 3,6)-β-D-Gal and (1 → 6)-β-D-Gal, which demonstrated DG2 was a novel galactoglucan and different from other fungal and botanic polysaccharide. Furthermore, DG2 did not contain deoxynivalenol, and showed no direct toxicity to human embryonic kidney cells and RAW 264.7 cells. Meanwhile, DG2 could increase the TNF-α, IL-6 and iNOs mRNA expression levels of RAW264.7 cells, and further promote the production of TNF-α, IL-6 and NO. These results suggested DG2 could enhance macrophage-mediated immune responses and have the potential to be an attractive functional food supplement candidate for the hypoimmunity therapies.

Biocatalysis has found enormous applications in sorts of fields as an alternative to chemical catalysis. In the pursue of green and sustainable chemistry, ionic liquids (ILs) have been considered as promising reaction media for biocatalysis, owing to their unique characteristics, such as nonvolatility, inflammability and tunable properties as regards polarity and water miscibility behavior, compared to organic solvents. In recent years, great developments have been achieved in respects to biocatalysis in ILs, especially for preparing various chemicals. This review tends to give illustrative examples with a focus on representative chemicals production by biocatalyst in ILs and elucidate the possible mechanism in such systems. It also discusses how to regulate the catalytic efficiency from several aspects and finally provides an outlook on the opportunities to broaden biocatalysis in ILs.

A newly immobilized Aspergillus niger lipase (ANL@ZnGlu-MNPs) was employed for the preparation of 1,2-epoxycyclooctane by oxidation of cyclooctene. The chosen variables, including substrate concentration, reaction temperature, immobilized enzyme dose, and H2O2 dose, were optimized in the reaction system of ethyl acetate. The yield and the enantiomeric excess of the product were achieved at 56.8% and 84.1%, respectively, under the following optimum reaction conditions: the concentration of substrate (cyclooctene) was 150 mM, the dosages of immobilized enzyme (ANL@ZnGlu-MNPs) and hydrogen peroxide were respectively 100 mg and 4.4 mmol, and the reaction was carried out in the system of 4 mL ethyl acetate at 40 &deg, C. Further study on the operational stability of ANL@ZnGlu-MNPs showed that more than 51.6% of product yield was obtained after reusing for ten batches. A novel immobilized lipase was prepared and applied to synthesize 1,2-epoxycyclooctane from cyclooctene. Although ANL@ZnGlu-MNPs performs well in operational stability and the reaction can achieve high enantiomeric purity of the product, the yield of the catalytic reaction needs to be further improved.

Food contamination caused by microorganisms has become a threat to consumers' health. Exploring antagonistic endophytes from plants of food raw-material and applying bioactive metabolites to inhibit the contamination has been an alternative and safer solution. In this study, we isolated and screened potential antagonistic endophytes from fresh Camellia assamica leaves, which were widely used in tea beverage production. We focused on a strain that showed visible inhibitory activity to Gram-positive bacteria, Gram-negative bacteria, and fungi. It was identified as a member of Bacillus velezensis and named FZ06. The results of genome analysis showed the strain FZ06 had 167 single-copy specific genes, much higher than those of most related strains. Also, 11 potential gene clusters of antimicrobial metabolites were found. Three groups of lipopeptides (surfactin, iturin, and fengycin) were identified by UPLC-MS/MS in purified antimicrobial methanol fraction of strain FZ06. The results of minimum inhibitory concentration (MIC) test proved the lipopeptide extract showed significant inhibitory effect on food spoilage bacteria (MIC 512−2048 μg/mL) and toxigenic fungi (MIC 128−256 μg/mL). In conclusion, this study suggests that the endophytic B. velezensis FZ06 and its lipopeptide extract hold great potential applications in the inhibition of food spoilage bacteria and toxic fungi in food industry.

In the study, the extraction, purification, identification and microencapsulation of anthocyanins from saskatoon berries were investigated. 4.48 ± 0.03 mg/ml of anthocyanins were obtained under the optimum extraction conditions that were 69% (v/v) acidified ethanol, 1:15 solid-liquid ratio and 3 times continuous extraction at 68 °C for 90 min. The AB-8 resin was selected to further purify and enrich anthocyanins based on its superior adsorption and desorption capacity. The purity of the obtained fraction by 80% acidized ethanol reached 92.1%, from which cyanidin-3-O-galactoside was identified by FTIR, LC-MS and NMR. In addition, microencapsulated anthocyanins, obtained using a deep eutectic solvent (DES), showed significantly improved stability in response to changes in light, oxygen, moisture content and pH. Further, as reaction media, DES could be recycled. The results showed that the present anthocyanins’ modification process could be used for the preparation of anthocyanins with a high purity and stability from berry fruits as well as other plants.

Magnetic nanocrystalline cellulose (MNCC) was prepared and used as an enzyme support for the immobilization of penicillin acylase (PA). A novel coupling agent, tri(hydroxymethyl)phosphine(THP) instead of the conventional glutaraldehyde(GA), was used as a crosslinker in this study. The obtained results showed that the immobilized PA with THP (PA-THP-MNCC) had high enzyme loading (172.3 mg/g) and activity recovery (77.6%) in the optimal preparation conditions, which were remarkably superior to those of the counterpart using GA (PA-GA-MNCC, 148.4 mg/g and 48.7%, respectively). Compared with free PA and PA-GA-MNCC, PA-THP-MNCC displayed a higher optimum pH and temperature, and manifested relatively higher enzyme-substrate affinity and catalytic efficiency. In addition, PA-THP-MNCC exhibited significantly enhanced stability. Furthermore, PA-THP-MNCC was successfully employed for synthesis of cefaclor, an important second-generation cephalosporin antibiotic, affording a significantly higher yield of 84% than that reported previously.

We found a novel lipase gene in the Paenibacillus pasadenensis CS0611 strain. The lipase gene sequence was cloned into the pET-28a expression vector to construct a recombinant lipase protein containing 6 × His tags at the C- and N-termini, respectively. High-level expression of the lipase in E.coli BL21 (DE3) was obtained upon induction with IPTG at 20 °C. The recombinant lipase activity was approximately 1631-fold higher than the wild type. His-tagged recombinant lipase was purified rapidly and efficiently by using Ni-charged affinity chromatography with 63.5% recovery and a purification factor of 10.78. The purified lipase was stable in a broad range of temperatures and pH values, with the optimal temperature and pH being 50 °C and 7.0, respectively. Its activity was stimulated to different degrees in the presence of metal ions such as Ca2+, Mg2+, and some non-ionic surfactants. In addition, the purified lipase was activated by a series of water-miscible organic solvents such as some short carbon chain alcohols and was highly tolerant to some water-immiscible organic solvents.

The extraction conditions and antioxidant activities of rutin from Sophora japonica bud by deep eutectic solvents were investigated. Box–Behnken design was used to optimize the extraction conditions and the scavenging activities of DPPH, O2− and ·OH of purified rutin were evaluated. The highest yield of 279.8 mg/g was achieved in the extraction medium of choline chloride/triethlene glycol (1/4) under the optimum conditions: water content of the DES 18.1%, extraction time 28.3 min, extraction temperature 70 °C and liquid–solid ratio 10 mg/1 g. The highest extraction amount was slightly different from the predicted value of the established second-order polynomial equation. In addition, The EC50 of DPPH scavenging, O2− scavenging and ·OH scavenging of rutin were 5.68 µg/mL, 0.19 and 0.28 mg/mL, respectively. The above results indicate rutin extracted by the choline chloride/triethylene glycol has excellent antioxidant activity and was an admirable free radical scavenger.

In order to obtain high-efficiency and sustainable adsorbents for both heavy metal ions and dyes, Millettia speciosa Champ cellulose and chitosan were used to prepare magnetic hydrogels with in-situ synthesis of Fe3O4 in this study. The results of characterization by vibrating sample magnetometer (VSM), Fourier transform infrared reflection (FTIR), X-ray diffraction (XRD), thermogravimetry analysis (TG and DTG), scanning electron microscope (SEM), mercury intrusion porosimetryand (MIP) and texture analysis indicated the magnetic hydrogels with high strength, high porosity and macroporous structure were successfully prepared, and they could be recovered by magnetic field. Besides, the prepared hydrogels had excellent adsorption effect on Cu2+ and Congo red (CR). The adsorption process for Cu2+ conformed to pseudo-first-order kinetics model better, whereas that for CR conformed to pseudo-second-order kinetics model better. Adsorption isotherm analysis showed that Freundlich model could better describe the adsorption process for both CR and Cu2+. The thermodynamic study results proved that the adsorption process for CR or Cu2+ was spontaneous and endothermic. Besides, the increase of pH had a negative effect on CR adsorption and a positive effect on Cu2+ adsorption. Adsorption mechanisms analysis revealed that electrostatic attraction and hydrogen bonding were involved in the CR adsorption, and amino groups acted dominantly in the process of Cu2+ adsorption. Furthermore, the prepared hydrogels exhibited excellent reusability, remaining their adsorption efficiency above 75% in five consecutive cycles. Therefore, the prepared hydrogels were expected to be promising materials for both heavy metal ions and dyes removal from waste water.

A composite zein nanofibrous mat containing fish oil and ferulic acid was successfully fabricated by electrospinning. The process became more fluent and continuous by adding 30 g/L glycerol into the polymer solutions and using modified coaxial electrospinning. The average diameter of nanofibers was 440 nm. The loading capacity and encapsulation efficiency of fish oil were 20% and 94%, respectively. FTIR data demonstrated that fish oil and ferulic acid were successfully embedded into the nanofibers and there were interactions among the molecules of zein, fish oil and ferulic acid. Addition of ferulic acid into the nanofibers significantly improved the oxidative stability of encapsulated fish oil; moreover, it did not change the release behavior of fish oil. The release of encapsulated fish oil was controlled by a combination of diffusion and macromolecular chain relaxation. This composite nanofibrous mat with favorable oxidation stability and release property is potential in application as nutrition additive.

An extracellular chitinase produced by Paenibacillus pasadenensis CS0611 was purified by ammonium sulfate precipitation, HiTrap DEAE FF and HiLoad 26/600 Superdex 200pg column chromatography. The apparent molecular mass determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis was 69 kDa. The optimum pH and optimum temperature of the chitinase were 5.0 and 50 °C, respectively. The enzyme showed high stability at alkaline pH values and temperatures below 40 °C. Additionally, the metal ions Mn2+, Mg2+, and Co2+ inhibited activity of the chitinase. The chitinase was active on colloidal chitin with an apparent Km of 4.41 mg/mL and Vmax of 1.08 mg/min. Substrate spectrum analysis indicated that the chitinase reacted preferentially with the glucosidic bond between GlcNAc-GlcNAc. The enzymatic hydrolysate was analyzed by high-performance liquid chromatography and thin layer chromatography, and clearly showed that a subunit of (GlcNAc)2 was the main hydrolysis product.

Cold-adapted pullulanase with high catalytic activity and stability is of special interest for its wide application in cold starch hydrolysis, but few pullulanases displaying excellent characteristics at ambient temperature and acidic pH have hitherto been reported. Here, a novel pullulanase from Bacillus methanolicus PB1 was successfully expressed in Escherichia coli BL21 (DE3) and determined to be a cold-adapted type I pullulanase (PulPB1) with maximum activity at 50 °C and pH 5.5. The recombinant PulPB1 showed great stability, its half-life at 50 °C was 137 h. PulPB1 can efficiently hydrolyze pullulan and amylopectin, with activities of 292 and 184 U/mg at 50 °C and pH 5.5, respectively. Moreover, the N-terminal domain of PulPB1 was found to significantly affect the enzymatic performance. Following truncation of the N-terminal domain, the activity towards pullulan decreased markedly from 292 to 141 U/mg and the half-life at 50 °C decreased from 137 to 10 h. Compared to the hydrolysis system with amyloglucosidase alone, the catalytic efficiency showed a 2.4-fold increase on combining PulPB1 with amyloglucosidase for amylopectin hydrolysis at 40 °C. This demonstrates that PulPB1 is promising for development as a superior candidate for cold amylopectin hydrolysis.

The asymmetric resolution of racemic 1-phenyl-1,2-ethanediol (PED) to (S)-PED by Kurthia gibsonii SC0312 (K. gibsonii SC0312) was conducted in a biphasic system comprised of an organic solvent and aqueous phosphate buffer. The impacts of organic solvents on the whole cell catalytic activity, metabolic activity, membrane integrity, and material distribution were first evaluated. The results showed that all organic solvents, except for dibutyl phthalate, showed a detrimental effect on the metabolic activity of the cells, especially for those with low log P values. All organic solvents were capable of changing the membrane permeability and membrane integrity of the cells. Moreover, some organic solvents showed a good extraction of the oxidation product. Finally, a high yield of 47.7 % of (S)-PED was obtained by the asymmetric resolution of racemic PED using K. gibsonii SC0312 in a biphasic system under the optimal conditions: racemic PED 120 mM, temperature 35 °C, reaction time 6 h, 180 rpm, and a volume ratio of dibutyl phthalate to aqueous phosphate buffer of 1:1. The optical purity of (S)-PED increased from 51.3 % to >99 %. This work described an efficient approach to improve reaction efficiency, and constructed a highly effective biphasic reaction system for the fabrication of (S)-PED via K. gibsonii SC0312.

Background Glucaric acid, one of the aldaric acids, has been declared a “top value-added chemical from biomass”, and is especially important in the food and pharmaceutical industries. Biocatalytic production of glucaric acid from glucuronic acid is more environmentally friendly, efficient and economical than chemical synthesis. Uronate dehydrogenases (UDHs) are the key enzymes for the preparation of glucaric acid in this way, but the poor thermostability and low activity of UDH limit its industrial application. Therefore, improving the thermostability and activity of UDH, for example by semi-rational design, is a major research goal. Results In the present work, three UDHs were obtained from different Agrobacterium tumefaciens strains. The three UDHs have an approximate molecular weight of 32 kDa and all contain typically conserved UDH motifs. All three UDHs showed optimal activity within a pH range of 6.0–8.5 and at a temperature of 30 °C, but the UDH from A. tumefaciens (At) LBA4404 had a better catalytic efficiency than the other two UDHs (800 vs 600 and 530 s−1 mM−1). To further boost the catalytic performance of the UDH from AtLBA4404, site-directed mutagenesis based on semi-rational design was carried out. An A39P/H99Y/H234K triple mutant showed a 400-fold improvement in half-life at 59 °C, a 5 °C improvement in $$ {\text{T}}_{ 5 0}^{ 1 0} $$ T 50 10 value and a 2.5-fold improvement in specific activity at 30 °C compared to wild-type UDH. Conclusions In this study, we successfully obtained a triple mutant (A39P/H99Y/H234K) with simultaneously enhanced activity and thermostability, which provides a novel alternative for the industrial production of glucaric acid from glucuronic acid.

Enzymatic catalysis in living cells enables the in-situ detection of cellular metabolites in single cells, which could contribute to early diagnosis of diseases. In this study, enzyme is packaged in amorphous metal-organic frameworks (MOFs) via a one-pot co-precipitation process under ambient conditions, exhibiting 5–20 times higher apparent activity than when the enzyme is encapsulated in corresponding crystalline MOFs. Molecular simulation and cryo-electron tomography (Cryo-ET) combined with other techniques demonstrate that the mesopores generated in this disordered and fuzzy structure endow the packaged enzyme with high enzyme activity. The highly active glucose oxidase delivered by the amorphous MOF nanoparticles allows the noninvasive and facile measurement of glucose in single living cells, which can be used to distinguish between cancerous and normal cells., For packaging enzymes into metal–organic frameworks (MOFs), crystalline MOFs are usually used. Here, the authors encapsulated enzymes in amorphous MOFs a via one-pot co-precipitation process under ambient condition, which led to higher enzymatic activity than in a corresponding crystalline MOF composite.

Recent progress in nanotechnology has provided high-performance nanomaterials for enzyme immobilization. Nanobiocatalysts combining enzymes and nanocarriers are drawing increasing attention because of their high catalytic performance, enhanced stabilities, improved enzyme–substrate affinities, and reusabilities. Many studies have been performed to investigate the efficient use of cellulose nanocrystals, polydopamine-based nanomaterials, and synthetic polymer nanogels for enzyme immobilization. Various nanobiocatalysts are highlighted in this review, with the emphasis on the design, preparation, properties, and potential applications of nanoscale enzyme carriers and nanobiocatalysts.

A support made of mussel-inspired polydopamine-coated magnetic iron oxide nanoparticles (PD-MNPs) was prepared and characterized. The widely used Aspergillus niger lipase (ANL) was immobilized on the PD-MNPs (ANL@PD-MNPs) with a protein loading of 138 mg/g and an activity recovery of 83.6% under optimized conditions. For the immobilization, the pH and immobilization time were investigated. The pH and thermal and storage stability of the ANL@PD-MNPs significantly surpassed those of free ANL. The ANL@PD-MNPs had better solvent tolerance than free ANL. The secondary structure of free ANL and ANL@PD-MNPs was analyzed by infrared spectroscopy. A kinetic study demonstrated that the ANL@PD-MNPs had enhanced enzyme-substrate affinity and high catalytic efficiency. The ANL@PD-MNPs was applied as a biocatalyst for the regioselective acylation of dihydromyricetin (DMY) in DMSO and gave a conversion of 79.3%, which was higher than that of previous reports. The ANL@PD-MNPs retained over 55% of its initial activity after 10 cycles of reuse. The ANL@PD-MNPs were readily separated from the reaction system by a magnet. The PD-MNPs is an excellent support for ANL and the resulting ANL@PD-MNPs displayed good potential for the efficient synthesis of dihydromyricetin-3-acetate by enzymatic regioselective acylation.

Artificial enzyme mimics have recently emerged as alternative biocatalysts for overcoming the intrinsic fragility of natural enzyme in practical applications. However, current researches regarding mimetic enzymes are still confined to very few reaction types, with artificial oxidoreductases as dominance. Herein, inspired by nature, we designed and fabricated a range of Zn-Triazole coordination polymers (ZnTazs) that presented similar coordination structures with the active site of natural carbonic anhydrase Ⅱ (CA Ⅱ). These synthesized compounds exhibited inherently mimetic function with natural CA for catalyzing the hydrolysis of p-nitrophenyl acetate (p-NPA). Especially, the initial hydrolysis rate (V0) of p-NPA catalyzed by ZnTaz-1 (Zn5(bta)6(NO3)4 · H2O) and ZnTaz-2 (Zn3(OH)2(btca)2 · DMF · 4 H2O) reached 42.1 and 73.8 nM · s−1, respectively. Meanwhile, ZnTaz-1 and ZnTaz-2 showed favorable recyclability, and excellent stability towards various pH values and organic solvents, which are of great significance for practical employment. Moreover, they could also promote the efficient hydration and sequestration of greenhouse gas CO2 in aqueous medium. Based on this work, we aim to provide more theoretical and practical basis for rational design of CA mimics from the inspiration of natural enzyme, as well as propose a potential strategy for tackling the CO2 crisis.

Highly efficient asymmetric reduction of 2-octanone to (R)-2-octanol catalyzed by immobilized Acetobacter sp. CCTCC M209061 cells was achieved in a biphasic system. Bioreduction conducted in aqueous single phase buffer was limited due to poor solubility and toxicity towards cells cause by product accumulation. Introduction of [C4MIM]·Ac accelerated the biotransformation process, giving 99% yield, >99% product e.e. and 1.42-fold higher initial reaction rate in conversion of 10 mM 2-octanone as substrate, compared with 99% yield, 97.3% product e.e. and 1.57 μmol min−1 of initial reaction rate in a aqueous single phase buffer system containing 6 mM 2-octanone as the optimal substrate concentration. Moreover, in the [C4MIM]·Ac-containing buffer/n-tetradecane biphasic system, the optimal substrate concentration was enhanced by 83 times (500 mM) in comparison with that in aqueous single phase buffer, resulting in 53.4% yield (267 mM), 99% product e.e. with 8.9 mM g-1 h-1 space time yield.

The extraction conditions and antioxidant activities of rutin from Sophora japonica bud by deep eutectic solvents were investigated. Box–Behnken design was used to optimize the extraction conditions and the scavenging activities of DPPH, O(2−) and ·OH of purified rutin were evaluated. The highest yield of 279.8 mg/g was achieved in the extraction medium of choline chloride/triethlene glycol (1/4) under the optimum conditions: water content of the DES 18.1%, extraction time 28.3 min, extraction temperature 70 °C and liquid–solid ratio 10 mg/1 g. The highest extraction amount was slightly different from the predicted value of the established second-order polynomial equation. In addition, The EC(50) of DPPH scavenging, O(2−) scavenging and ·OH scavenging of rutin were 5.68 µg/mL, 0.19 and 0.28 mg/mL, respectively. The above results indicate rutin extracted by the choline chloride/triethylene glycol has excellent antioxidant activity and was an admirable free radical scavenger. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s13197-018-3151-9) contains supplementary material, which is available to authorized users.

Different kinds of low transition temperature mixtures (LTTMs) were synthesized with DL-lactic acid and five different quaternary ammonium salts respectively, and their viscosity and solubility parameters change with different molar ratios of quaternary ammonium salt to DL-lactic acid were investigated and compared with anthocyanins. Then the LTTMs synthesized were used to extract anthocyanins from saskatoon berry (Amelanchier alnifolia Nutt.). It turned out that the choline chloride/DL-lactic acid (ChCl/LA) showed the best solubility of anthocyanins compared with the other LTTMs, which was in line with solubility parameter theory. Under the optimized process condition with 1 : 15 of molar ratio, 1 : 20 of solid to liquid ratio, 50 °C of extraction temperature and 45 min of extraction time, the extraction amount of anthocyanins reached 525.27 ± 0.82 mg per 100 g and the extracted rate of anthocyanins was 87.4%. Then the macroporous resin AB-8 adsorbent was used to separate and purify the anthocyanin compounds from saskatoon berry, with a recovery yield of 65.7%. Further, the confirmation of the purified anthocyanins was carried out using nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FT-IR) and high performance liquid chromatography-mass spectrometry (HPLC-MS). Finally, the purified anthocyanins were proved to be good antioxidants through the comparison with vitamin C and butylated hydroxytoluene.

Dihydromyricetin is the principle component of the Chinese herbal tea Teng-cha and a promising ingredient for functional food and nutraceuticals, but its low solubility limits its application potentials. This study explored enzymatic acylation of dihydromyricetin to improve its solubility in lipid systems. Acylation was achieved with several lipases with the synthesis of a major (86%) product and a minor product. Isolation and purification of the products by preparative HPLC followed by LC-MS, (13)C NMR, (1)H NMR and 2 D-HSQC NMR analyses showed that the major product was a dihydromyricetin monoester with the acylation site at the 3-OH group of C ring. Quantum chemical calculations revealed that the 3-OH had the lowest antioxidant activity, and therefore acylation at this site was expected to have minimum impact on the antioxidant activity. Several factors, including solvent, acyl donor, enzyme origin, molar ratio of substrates and reaction temperature and time, exhibited significant effects on the initial rate, conversion yield and regioselectivity of the reaction. Acylation occurred only with vinyl acetate as the acyl donor, and highest conversion yields were achieved with immobilized Penicillium expansum lipase and Novozyme 435 with DMSO and acetonitrile being the best solvents. In general, the acylation results were found to be superior to previous reports on acylation of aglycone flavonoids with respects to conversion yield and regioselectivity.